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Repro > Week 2.2 - The menstrual cycle > Flashcards

Week 2.2 - The menstrual cycle Flashcards

1
Q

In general, What effects do oestrogen have on the gamete and the endometrium?

A
  • Prepare the gamete for ovulation

- Prepare the endometrium for implantation

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2
Q

What is the function of the luteal phase?

A

-Hold the system in pause and maintain the endometrium until a signal is received that fertilisation has happened

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3
Q

In what rhythm is GnRH released?

A

-Pulsatile release every hour

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4
Q

What are the functions of FSH and LH in the female?

A
  • Promote follicular development
  • Stimulate follicular cells to produce steroid hormones and inhibin
  • ovulation
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5
Q

What control do the gonadal hormones have upon HPG axis?

A

-Both positive and negative feedback

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6
Q

When does oestrogen have positive feedback effects?

A

-When it is high titres by itself ie the follicular phase

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7
Q

When does oestrogen exert negative feedback?

A

-When it is at moderate titres ie luteal phase

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8
Q

What is the dominant steroid hormone in the luteal phase?

A

-Progesterone

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9
Q

Describe the ovarian steroid hormone levels at the start of the cycle

A

-No ovarian hormone production

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10
Q

Which hormone encourages follicular development at the start of the cycle?

A

-FSH

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11
Q

Why is it that ovarian hormones drop at the end of the cycle? What effect does this have on the HPG axis?

A
  • Follicular cells are dying and thus stop producing oestrogen/progesterone
  • This resets the HPG axis as all feedback is removed as the levels are too low.
  • GnRH can now work normally, causing slow release of FSH and LH
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12
Q

What effect does resetting the HPG axis have on the ovary?

A

-Recruitment of small group of follicles within ovary independent of extragonadal signals. This starts follicular development

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13
Q

Which cells of the ovary do FSH act on?

A

-Granulosa cells

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14
Q

When does oestrogen secretion become possible from the developing follicle? Why?

A
  • When theca interna has developed -> has LH receptors

- Oestrogen production depends on interaction between theca and granulosa cells

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15
Q

What hormone, besides oestrogen, begins to be secreted from the developing follicle?

A

-Inhibin

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16
Q

What drives the formation of a dominant follicle? (2 things)

A
  • Follicular oestrogen now at a level where it can exert a positive feedback control at the hypothalamus and pituitary
  • Follicular inhibin levels rise which selectively inhibits FSH production by anterior production
17
Q

What is the consequence on gonadotropin levels of inhibin?

A

-Only see a rise in LH, FSH secretion inhibited

18
Q

There is a rapid rise in oestrogen and inhibin at approximately day 12 (when the follicle is fully developed), what effect does this have on gonadotropin hormones?

A

-LH surge

19
Q

Why does progesterone production begin after LH surge?

A

-Granulosa cells become responsive to LH as prior to this they only had FSH receptors

20
Q

What effect does oestrogen exhibit on the sensitivity of anterior pituitary?why does this cause the LH surge?

A
  • High levels of oestrogen increases sensitivity of anterior pituitary to GnRH
  • Early follicular phase -> Oestrogen low-> anterior pituitary not very sensitive to GnRH -> slow release of LH
  • Late follicular phase ->oestrogen high-> sensitivity of the anterior pituitary is increased -> LH surge.
21
Q

How does LH contribute to ovulation?

A
  • Causes increase in collagenase activity -> follucle membrane breakdown -> oocyte released
  • Causes PG increase -> contraction of ovarian wall to help extrusion
22
Q

What happens to the primary oocyte in the follicle just before ovulation?

A

-Meiosis 1 completes and meiosis II starts

23
Q

What happens to the follicle after ovulation?

A

-Remains in the ovary and become leutinised under the control of LH (forms corpus luteum)

24
Q

What is the function of the corpus luteum?

A
  • Secrete oestrogen and progesterone from androgens in large quantities
  • Inhibin still pruduced to inhibit FSH
  • Suppresses LH secretion by putting the axis into pause as further gamete development is suspended due to negative feedback of oestrogen and progesterone
25
Q

What happens to the corpus luteum in the absence of LH?

A

-Spontaneous regression

26
Q

What happens to the hormone profile after the corpus luteum has regressed?

A

-The axis is reset and everything is at basal levels

27
Q

What happens to the corpus luteum if fertilisation occurs?

A

-Syncytiotrophoblast produces hCG which has luteinising effect and maintains the corpus luteum until the placenta is sufficiently developed to take over oestrogen and progesterone production to control HPG (approx 4 months)

28
Q

What are the two phases in ovarian cycle?

A
  • Follicular

- Luteal

29
Q

What are the two phases in the uterine cycle?

A
  • Proliferative

- Secretory

30
Q

What causes the proliferation of the endometrium?

A

-Oestrogen produced from ovary

31
Q

What effect does progesterone have on the endometrium?

A

-Causes it to enter the secretory cycle where it becomes very glandular to allow implantation

32
Q

What effect does oestrogen have in the follicular/proliferative phase?

A
  • Increases mobility of uterine tube
  • Thickening of endometrium
  • Growth and motility of myometrium
  • Thin alkaline cervical mucus
  • Vaginal changes
  • Changes in skin, hair and metabolism
33
Q

What effect does progesterone have in the luteal/secretory phase?

A
  • Further thickening of the endometrium to become glandular
  • Thickening of myometrium but reduces motility
  • Thick acid cervical mucus
  • Changes in mammary tissue
  • Increases in body temperature
  • Metabolic and electrolyte changes
34
Q

Why in the luteal phase, does the cervical mucus become thick and acidic?

A
  • Limit polyspermy

- Prevent infection

35
Q

What is the normal limit for menstrual cycle? How can it vary?

A
  • 21-35 days

- Luteal phase always 14 days (+/- 2 days) it is the follicular phase which varies

36
Q

What is the ovarian cycle?

A

-Preparation of the gamete for ovulation

37
Q

Describe the relationship between theca interna and granulosa cells in producing oestrogen

A
  • Theca interna has receptors for LH which causes the production of androgens (androstenedione) which are precursors of eostrogen
  • Granulosa cells have the enzyme aromatase which use the androgens secreted by theca interna to oestrogens

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